The ability to manipulate, control, and/or modify (collectively, “modify”) a fluid flow is important for increasing the performance of, or otherwise altering, a fluid system. Some previous attempts to modify fluid flows have focused on passive flow controls (i.e., where an input of external energy is not required). Some of the known passive controls include boundary layer trips, roughness elements, ejector nozzles, and surface perturbations. These passive controls often create turbulence or disruption in the fluid flow. Since these passive methods do not include any form of external energy input, they do not allow for activation and deactivation of the control. This limits the amount of flow control and does not allow a user to manipulate the flow as desired.
To increase the amount of control, other attempts to modify fluid flow have focused on active flow controls (i.e., requiring an input of external energy). These types of controls enable a user to activate and deactivate the flow control, as desired. Some examples of these controls include acoustic excitation, continuous or pulsed suction and blowing, and surface motion. Similar to the passive controls, these create a turbulence or disruption in the fluid flow. Unfortunately, these active flow controls require moving parts, such as diaphragms or pumps to effectuate the flow control. Over time, these moving parts can fail. Other types of active flow controls require a structure that projects into the fluid flow. This projection can disturb the fluid flow over a surface. For instance, in certain aerospace designs, it is undesirable to have a structure projecting into the air flow. Such structures can negatively impact the desired lifting or other properties of the aerospace structure.
Accordingly, a fluid actuator is needed that can modify a flow of fluid without the need for moving parts. The actuator would allow for activation and deactivation, as desired. The actuator would also be capable of being mounted substantially flush with a surface, such that it may modify the flow without significantly projecting into it. The actuator would also be able to operate as a synthetic jet (such as, an actuator that injects fluid with zero net mass but finite momentum) for directing flow away from the actuator, as well as a suction device for directing flow toward the actuator.